I have a good question. Lets pretend im using acl bearings for my setup.
my question is, are the material for the upper and lower ROD bearings the same? I couldnt see any difference between the two beside the U for upper and L for lower.
My next question is, what would happen if you were to mix up the two? For example, what if you put the lower on the upper and the upper on the lower?
Hmm..

if you have any insights on this please let me know. thank you.

 

It's not the material that varies but the location of the chamfer and the locating tang. I'm not that familiar with ACL bearings but they should be the same for upper and lower.